Platinum-coated nanotube biosensor detects glucose in near real time

Researchers at the University of Arkansas have fabricated a novel
biosensor that detects glucose in close to real time and with much greater
sensitivity than other comparable, biocompatible sensors.

The sensor, designed and developed by Jining Xie and researchers in the
Department of Electrical Engineering, is made of multi-walled carbon
nanotubes coated with platinum nanoparticles 1-5 nanometres in diameter. The
researchers tested sensors with and without the platinum nanoparticles, and
discovered that the carbon nanotubes with platinum exhibited a substantially
higher sensitivity than those without platinum.

Carbon nanotube coated with
platinum

“To manage and control diabetes, patients must continuously monitor
blood-glucose levels, so they understand the importance of a device that
provides rapid response," said Jining Xie, research assistant professor of
electrical engineering. "At this stage of the research, we believe that the
improved electro-chemical performance is due to the platinum nanoparticles.
We are currently investigating mechanisms to optimize this performance.”

The research was carried out in the university’s Nanomaterials Research
Laboratory by Xie and Vijay Varadan, Distinguished Professor of Electrical
Engineering. Shouyan Wang, post-doctoral fellow, and Lavanya Aryasomayajula,
graduate assistant, also contributed to the project.

Tests revealed that for every square centimetre tested, a typical
platinum-coated nanotube-based glucose sensor had a sensitivity of around 50
micro-amps per milimole (milimoles are a measure of molecular concentrations
of glucose). The sensitivity value of the researchers’ device is among the
best results reported for glucose biosensors.

Xie said their goal is to further increase the sensitivity value of 52.7
micro-amps per milimole. Equally important, the biosensor has a response
time of 15 to 30 seconds, which renders it capable of providing glucose
screenings close to real time.

The researchers attributed the improved sensibility to various factors
related to the application of platinum to the multi-walled nanotubes. Most
importantly, the platinum nanoparticles created a larger electro-active
surface area on the carbon nanotubes. The larger surface area allowed the
carbon nanotubes to act as a glucose-oxidase reservoir, which helped create
uniform immobilization and high loading of glucose oxides for sensing. In
addition, the platinum nanoparticles enhanced electron transfer and
facilitated better physical and chemical bonding between glucose oxides and
carbon nanotubes.

The findings were published in the February issue of Nanotechnology,
The article is
available online.

Professor Varadan said that there had been no previous research on the
use of platinum nanoparticles coated on carbon nanotubes to develop a
biosensor capable of detecting blood-glucose concentrations.

The research is sponsored by NeoPharma Industries, which hopes to develop
a commercial product by the end of 2007.